The invention relates to apparatus for deactivating a limited number of cylinders in a multi-cylinder internal combustion engine.
Automotive engines have the ordinarily conflicting demands of providing high power capacity and good fuel economy. To achieve these needs, intake and exhaust valve deactivation to turn off some of the cylinders in a V-8 or V-6 engine has been attempted for a number of years. In the past, this approach has not been fully successful with consumers because the ability to rapidly respond to a vehicle""s power needs has not always been reliable. With the evolution of a multitude of sensors in modern vehicles and the centralization of inputs from these sensors into the engine control module, a potential to execute this valve deactivation strategy in an engine exists.
To implement this strategy in a V-8 engine, up to four of the cylinders are deactivated at one time to effectively change the engine from a V-8 to a V-4. This reduction in the number of cylinders which are working results in reduced fuel consumption and hence improved fuel economy. The cylinders are turned off by locking the inlet and exhaust valves into the closed position. This stops air from entering or exiting the cylinders and by not turning on the fuel injectors, the cylinders are completely turned off. The inlet and exhaust valves are locked into the closed position by advancing a pin through the valve which mechanically holds the valves closed. This pin force is balanced by hydraulic pressure on one end and a coil spring on the other. A need exists for an economical, reliable and compact system for deactivating and reactivating the valves through these pins in a nearly instantaneous manner.
The invention provides an electro-hydraulic control module for deactivating sets of intake and exhaust valves in an internal combustion engine. The invention provides a module that is small in size, particularly in height, and is economical to manufacture and in operation is fast, reliable, and repeatable. The module employs relatively thin plates to provide hydraulic flow paths and to carry the hydraulic valve elements and actuating solenoids.
More specifically, the plates include so called xe2x80x9cworm trailsxe2x80x9d or passages that transmit supply, exhaust, and control pressures to and from the control valves. The plates, which can be conveniently bolted across the top plane of the central valley of a V-shaped engine block such as in a V-8 engine, suspend the actuating solenoids in the valley space. The disclosed hydraulic valves, one for each engine cylinder to be deactivated, are located in low profile multiple purpose plate structures and use an inexpensive spherical ball as the valving element.
In each of the disclosed embodiments, the solenoids are electrically connected with conductors carried in a common rigid connector frame to simplify assembly procedures and reduce costs.
The invention provides a novel bleed circuit for reducing and, preferably, eliminating air from the hydraulic control passages in the module and the so-called xe2x80x9cpin towersxe2x80x9d in the engine that lead to the intake and exhaust valve disabling pin elements. The reduction in air in the control passages greatly improves the speed and repeatability of the hydraulic circuit. Speed and repeatability are important in the application of the present invention, because only a very short time is available with the engine running at moderate or high speed when the valves are motionless and thereby susceptible to be mechanically disabled in a shockless, i.e. smooth, manner. Repeatability or predictability of function of the disclosed circuitry of the module of the invention enables an engine control module to anticipate when the engine valves will be stationary and to initiate hydraulic valve actuation in the electro-hydraulic module at an appropriate time before then to assure that the hydraulic functions are completed within the available time.